Understanding and Managing Pecan Bacterial Leaf Scorch Southeastern - PowerPoint PPT Presentation

Understanding and Managing Pecan Bacterial Leaf Scorch Southeastern Pecan Growers Association Convention Destin, Florida • February 26-27, 2016 Rebecca A. Melanson , Extension Plant Pathologist Central MS Research and Extension Center • Raymond, MS

A Bit of History Disease first recognized in 1972 • Identified as a bacterial disease • and named pecan bacterial leaf scorch (PBLS) in 2000 Xylella fastidiosa subsp. • multiplex (2012) • Lives in the water-conducting tissues (xylem) of the plant PBLS in ‘Cape Fear’ pecan.

PBLS Symptoms ‘Early’-stage PBLS symptoms. Late-stage PBLS symptoms.

PBLS Symptoms PBLS in a young grafted tree. PBLS in a mature tree.

Cultivar Susceptibility *Barton Elliott Moreland Shoshoni Caddo Farley Navaho Stuart *Cape Fear Forkert Nacono *Sumner Candy Jackson *Oconee Woodman Cherokee Kiowa *Pawnee *Cheyenne Mahan *Rome Natives/seedlings Desirable Melrose Schley NO RESISTANT CULTIVARS HAVE BEEN IDENTIFIED. *Highly susceptible cultivars. Reference: Sanderlin, 2005, Plant Disease 89:446-449.

Effect of PBLS on Yield and Tree Growth Time % Leaflet % Reduced % Reduced Period Defoliation Kernel Weight Nut Weight Year 1 67 19 29 Yield Year 2 66 16 32 Year 3 41 14 20 Average 58 16.3 27 Age of Trees % Less Diameter % Less Height Tree 4 Years Old 43 40 Growth 9 Years Old 52 N/A References: Sanderlin and Heyderich-Alger, 2003, Plant Disease 87(3):259-262 .; Sanderlin, unpublished

Graft Transmission in Pecan • Infected scions – 21% transmission rate • Infected rootstocks – 85% transmission rate PBLS in new growth from infected scion. References: Sanderlin and Melanson, 2008, Plant Disease 92:1124-1126.; Sanderlin and Melanson, 2006, HortScience 41(6):1455-1456.

Hot-water Treatment of Scions Identified PBLS-infected limbs. Prepared scions for storage. Bundled scions with a weight. Treatment • 115ºF water for 30 min • Room temperature water for 1-2 min Completely submerge! Grafted to non-infected rootstock. Submerged scions in hot water. The link to the publication “Procedure for Hot Water Treatment of Pecan Scion Wood” can be found at the end of this presentation.

Hot-water Treatment of Scions At a 21% graft-transmission 100 % Graft-transmission of X. fastidiosa # of X. rate, 29 of the 140 hot- # of # of Trees Two-Year % Graft fastidiosa- Scions with PBLS 80 water-treated scions Totals Success Infected Tested Symptoms Trees should have been infected. 60 **97% EFFECTIVE** Hot-water 165 84.8 2 1 Treated Scions 40 21.3 Non-treated 20 105 84.7 18 19 Scions 0.7 0 Hot-water-treated Non-treated scions scions Reference: Sanderlin and Melanson, 2008, Plant Disease 92:1124-1126.

PBLS Spread in a Mature Orchard • Orchard location: Number of Diseased Trees/Number of Year LSU AgCenter Pecan Trees in Orchard (% Infected Trees) 2001 5/410 (1.2%) Research-Extension 2002 12/410 (2.9%) Station, Shreveport, 2003 17/409 (4.2%) Louisiana 2004 33/390 (8.5%) • Planting date: 2005 63/390 (16.2%) 1986 or 1987 2006 91/390 (23.3%) • Composition: An increase in the number of PBLS-infected trees was observed in all cultivars and in most non-grafted trees. – 3 cultivars and non- However, the greatest increase in the number of infected grafted trees trees occurred in cultivar Cape Fear, the cultivar in the – 5 rootstocks orchard with the highest susceptibility.

Insect Transmission in Pecan Collected potential vectors – Fed captured insects on infected xylem-feeding insects pecan tissue and then caged them (spittlebugs and sharpshooters). onto Cape Fear pecan seedlings.

Insect Transmission in Pecan • Percent transmission varied from 2% – 100% depending on the insect species Johnsongrass sharpshooter Pecan spittlebug (adult) Lateral-lined sharpshooter 100% 19.6% Glassy-winged sharpshooter Diamond-backed spittlebug 2 – 11.4% 16.7% 4% Photos by: S. Gil Photo by: R. Melanson Reference: Sanderlin and Melanson, 2010, Plant Disease 94(4):465-470.

Monitoring Pecan Orchards for Vectors* Orchard locations: Dr. R. S. Sanderlin at the LSU AgCenter Pecan Research-Extension Station in Shreveport, LA, has monitored five pecan orchards in Louisiana for the presence of known and potential vectors of Xylella fastidiosa using yellow sticky traps . Data indicated that the greatest number of known and potential vectors were present in orchards from May through August. *Known and potential vectors

Subspecies of Xylella fastidiosa • Subspecies fastidiosa (2004) – Almond, grapevine • Subspecies multiplex (2004) – Almond, peach, oak, pecan • Subspecies pauca* (2004) Bacterial leaf scorch in pin oak Pierce’s disease J. Hartman, Univ. KY, Bugwood.org A. H. Purcell, Univ. CA - Berkeley, Bugwood.org – Citrus, coffee • Subspecies sandyi (2005) – Oleander • Subspecies tashke (2009) – Chitalpa Citrus variegated chlorosis* Bacterial leaf scorch in sycamore *Not currently present in the U.S. A. H. Purcell, Univ. CA, Bugwood.org T. D. Leininger, USDA Forest Service, Bugwood.org

Management of PBLS • FOCUSED ON PREVENTION! • Plant non-infected trees • Use non-infected rootstock • Collect scion wood from non-infected trees • Hot-water treatment of scions • Monitor vectors in orchards and apply insecticides during peak trapping periods or at first appearance (?) • Avoid planting/remove plants near orchards that attract vectors OR manage vectors on those plants (?) • Branch or tree removal (?)

Thank you for your attention! • Rebecca A. Melanson Extension Plant Pathologist Central Mississippi Research and Extension Center Mississippi State University Phone: (601) 857-2284 Email: rebecca.melanson@msstate.edu • R. S. Sanderlin Photo by MSU Extension Research/Extension Plant Pathologist The research discussed in this presentation was conducted by LSU AgCenter Pecan Research-Extension Station R. A. Melanson and R. S. Sanderlin at the LSU AgCenter Louisiana State University Pecan Research-Extension Station or at Louisiana State University. Unless otherwise specified, photographs were taken Email: RSanderlin@agcenter.lsu.edu by R. A. Melanson or R. S. Sanderlin.

Additional Resources • Articles: – Pecan Bacterial Leaf Scorch Cultivar Susceptibility and Pathogen Transmission – Pecan Bacterial Leaf Scorch: A New Look at an Old Problem – Procedure for Hot Water Treatment of Pecan Scion Wood • Additional photos of PBLS (search ‘ Xylella fastidiosa and pecan’) – www.ipmimages.org/

PBLS Research Publications Melanson, R. A. and Sanderlin, R.S. 2015 . Hot-water treatment of pecan scions as a means of phytosanitation to reduce the potential introduction of • Xylella fastidiosa , the causal agent of pecan bacterial leaf scorch, into orchards and new geographic regions. Acta Horticulturae 1070:201-209. Melanson, R. A., Sanderlin, R. S., McTaggart, A. R. and Ham, J. H. 2012 . A systematic study reveals that Xylella fastidiosa strains from pecan are • part of X. fastidiosa subsp. multiplex . Plant Disease 96:1123-1134. Li, B., Sanderlin, R. S., Melanson, R. A., and Yu, Q. 2011 . Spatial analysis of a plant disease in a non-uniform crop: a Monte Carlo approach. Journal • of Applied Statistics 38(1):175-182. Sanderlin, R. S. and Melanson, R. A. 2010 . Insect transmission of Xylella fastidiosa to pecan. Plant Disease 94(4):465-470. • Sanderlin, R. S., Li, B., Melanson, R. A., and Gil, S. 2009 . Spread of Xylella fastidiosa in a pecan orchard and presence of potential vectors in • orchards. Phytopathology 99:S114. (abstract) Sanderlin, R. S. and Melanson, R. A. 2008 . Reduction of Xylella fastidiosa transmission through pecan scion wood by hot-water treatment. Plant • Disease 92:1124-1126. Sanderlin, R. S. and Melanson, R. A. 2006 . Transmission of Xylella fastidiosa through pecan rootstock. HortScience 41(6):1455-1456. • Sanderlin, R. S. 2005 . Cultivar and seedling susceptibility to pecan bacterial leaf scorch caused by Xylella fastidiosa and graft transmission of the • pathogen. Plant Disease 89:446-449. Sanderlin, R. S. and Heyderich-Alger, K. I. 2003 . Effects of pecan bacterial leaf scorch on growth and yield components of cultivar Cape Fear. Plant • Disease 87(3):259-262. Sanderlin, R. S. and Heyderich-Alger, K. I. 2000 . Evidence that Xylella fastidiosa can cause leaf scorch disease of pecan. Plant Disease 84 (12): • 1282-1286. Sanderlin, R. S. 1998. Evidence that Xylella fastidiosa is associated with pecan fungal leaf scorch. Plant Disease 82:264. •